Antihalation coating



March 10, 1942. c, FQRDYQCE r 2,275,817 Q ANTIHALATION comma Filed Jan. 18, 1941 F/sQ/ ANT/HALAT/ON BACK/N6 OF GUM ARAB/C PHTHALA TE.

OVERCOATl/YG 0F GUMARAB/C LAYER 0F GUM ARAB/C PHTHALATE.

DYE LAYER.

CHARLES R. FORDYCE JoH/v EMERSON I INVENTOR-S BY (8. EMMMM ATTORNEYS Patented Mar. 10, 1942 I I i g UNITED STATES PATENT OFFICE Charles R. Fordyce and John Emerson, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application January 18, 1941, Serial No. 375,052

8 Claims. (Cl. 95-9) This invention relates to photographic film and added to precipitate the gum arabic. The gum is particularly to coatings to be applied thereto for filtered ofi with suction and then washed with 500 various purposes, such as for preventing halaparts of pyridine and again filtered oil. The tion. weight of the cake is approximately 780 grams.

Use has previously been made of film-forming 6 The resulting cake is treated with 216 parts of materials such as cellulose acetate phthalate for pyridine and 1500 parts of phthalic anhydride. anti-halation film backings, for which purpose The reaction mixture is heated on a steam bath these materials are particularly useful by virtue for 6 hours at 90 C. At this point an additional of their selective solubility, being insoluble in wa- 100 parts of phthalic anhydride is added and the ter but convertible to water-soluble alkali salts l heating continued for one hour more. There'- in the photographic processing baths. The celsulting light brown colored solution is diluted lulose acetate phthalate does not dissolve in the with 500 parts of distilled water and precipitated developing bath because of a salting out effect with stirring in distilled water acidified with 750 but is rapidly removed when introduced in the parts of 36% hydrochloric acid. The white powwash water which follows. dery precipitate is filtered OE and washed with One of the objects of the present invention is distilled water. The product may be further to provide a hovel antihalation backing or propurified by dissolving it in a 1:1 mixture of acetective coating for photographic film. A further tone and methyl alcohol and reprecipitating in object is to provide an antihalation backing or distilled water. The product contains 62% protective coating which is readily soluble in 2.1- phthalyl. It is soluble in the following solventsi kaline solutions, such as photographic developers. methyl, ethyl, and propyl alcohols; fl-methoxy- In the accompanying drawing Fig. 1 is an enethyl alcohol; fl-ethoxyethyl alcohol; ethylene larged sectional view of a photographic film havglycol monoacetate; ethylene formal. ing an anti-halation backing made according to This product may be applied in the known -our invention, Fig. 2 is an enlarged sectional view manner, which may be either application of a of a photographic film having an overcoating sub layer of the gum arabic phthalate to. the layer made according to our invention, and Fig. photographic support followed by application of 3 is 'an enlarged sectional view of a film having a suitable dye solution, or preparation of a sub' separate backing layers of alkali soluble material composition containing both the gum arabic and dye. phthalate and the dye which is coated on the Wehave found that dicarboxylic acid esters of film support in one application. Suitable solvent v gum arabic, such as gum arabic phthalate and mixtures for such applications depend upon the gum arabic succinate are suitable for use as overfilm support to which it' is being applied (cellucoating and backing layers for photographic film, lose acetate, cellulose nitrate or mixedesters of and that they may contain an antihalation or cellulose are satisfactory). In general, mixtures filter dye, or may be coated on a.film and overcomposed largely of methyl or ethyl alcohol concoated with a dye solution. These materials are taining minor quantities of acetone or methyl coated in solution as the free acid ester and upon cellosolve will be found most suitable. treatment of the film in alkaline solution, such Gum arabic succinate may be prepared in a as photographic developing solutions, an alkali similar manner. Fifty grams of gum arabic were metal salt of the phthalate is formed and this dissolved in 100 g. of warm distilled water. After. compound dissolves freely in the solution. The solution, the water was displaced by pyridine. um arabic phthalate or succinate itself is not The pressed cake consisting of 50 g. of gum arabic soluble in water but must be coated from a suitand 40 g. of pyridine was treated with 160 g. of able solvent solution. pyridine and 100 g. of succinic anhydride. This The gum arabic dicarboxylic acid este are mixture was stirred and heated at 85 C. for four pr pared y t at n gum a abic w a d a hours. At the end of this period, the product xyli a i anhydri e in he Pr s of a was recovered by dilution of the dope with acetic tia y o ani bas su h as pyridine in a manner acid and precipitation of the ester in acetone'. similar to that described in Malm and Emerson o invention 111 n be described with r'ef- U. S. 2,211,338, granted August 13, 1940. Gum erence to theaccompanyin drawing. As shown arabic p t a ate ma b pr par d as ws: therein, Fig. 1 is asectional view of a-fllm sup- To 500 parts of gum arabic are added 500 parts port It of glass, cellulose nitrate, cellulose aceof distilled water with stirring. A mixture of 500 tate, synthetic resin or other suitable material v parts of pyridine and 500 parts of acetone is then having thereon an emulsion layer II. The opcoating of gum arabic phthalate with or without dye may also be applied to the reverse side of the film or plate.

Fig. 3 shows another modification of our invention in which the support I having an emulsion layer II on one side thereof is coated on the opposite side with a layer of gum arabic phthalate i4 not containing a dye and a layer l5 of dye coated from a solution of water or organic solvent is laid over the gum arabic phthalate layer ll.

Our invention will be more specifically described by means of the following examples which are illustrative only.

EXAMPLE I Twenty grams of gum arabic phthalate was dissolved in 80 g. of a mixture of 70 parts of methyl alcohol and 30 parts of ethylene glycol monomethyl ether. The solution had a density of 0.91 and a viscosity of 10.2 centipoises. A thin coating of this solution was applied to the surface of a cellulose acetate propionate film base,

and while still containing some solvent was tinted coating of this solution is applied to the surface of a cellulose nitrate film base, and the solvent removed by curing. The resulting tinted layer was removable during processing in alkaline so-' lutions.

Exsurtr: II

A solution was made of g. of gum arabic succinate, 37 g. of ethyl alcohol and 1.25 g. of an organic solvent-soluble dye such as nigrosine. This solution was applied evenly to a roll of cellulose nitrate film base. The material was cured to produce aglossy anti-halation backing which In every case the amount of coloring material is adjusted to give the desired density in the final coating. For antihalation eflects the density should be approximately 0.2 expressed as a logarithm to the base 10, whereas a density greater or less than that may be required depending upon what use is made of the coating.

It is apparent from the above invention that our antihaiation layers may consist of one, two or more separate coatings or layers and that the dyes may be contained in one or more of the layers. By the term "anti-halation layer it is understood that we include any of these combinations whetherone or more actual layers are contained in the coating.

Coatings of dicarboxylic acid esters of gum arabic have a number of favorable characteristics. In addition to forming a suitable carrier or supporting layer for an antihaiation or filter dye.

. which is readily removed in photographic develwas completely removable during film processon the opposite side thereof.

opers, they are resistant to moisture. An overcoating layer of a dicarboxyllc acid ester of gum arabic, therefore, protects. the film or the emulsion from the action of moisture and also may serve as a protective coating to avoid scratches and abrasion marks on films or plates. Numerous variations may be made in the coating solutions, solvents, dyes and other features of our invention and it is to be understood that the invention is to be taken only by the scope of the appended claims.

What we claim is:

1. A transparent photographic element comprising a support, a sensitive emulsion layer thereon, and a layer of a dicarboxylic acid ester of gum arabic thereon.

2. A transparent photographic element comprising a support, a sensitive emulsion layer on one side thereof, and an antihaiation layer containing a dicarboxylic acid ester of gum arabic 3. A transparent photographic element com- .prising a support, a sensitive emulsion layer on one side thereof, and ,an antihalation layer .of

gum arabic phthalate on the opposite side thereof.

4. A sensitive photographic element comprising a cellulosic support, an emulsion layer on one side of said support and an antihalation layer of a dicarboxylic acid ester of gum arabic and a coloring material on the opposite side thereof.

5. A sensitive photographic element compris ing a cellulose support, an emulsion layer on one side of said-support, and an antihalation layer of a dicarboxylic acid ester of gum arabic and a dye on the opposite side thereof.

6. A sensitive photographic element comprising a cellulosic support, an emulsion layer on one side of said support, and an antihalation layer of a dicarboxylic acid ester of gum arable and carbon on the opposite side thereof.

"l. A sensitive photographic element comprising a support. a sensitive emulsion layer. on said support and a protective coating of a dicarboxylic acid ester of gum arabic over the emulsion layer. 8. The method of providing a photographic element with an antihalation coating which comprises dissolving gum arabic phthalate in a nonaqueous solvent, coating the solution on the back face of the element, and coating a coloring material over the gum arabic phthalate layer.

, CHARLES R. FYORDYCE;

JOHN mason. 

